More carbon is stored in boreal forests than any other type of forest, but that’s changing with increasingly frequent and severe wildfires.
More than four years after a wildfire burned more than ten times the annual mean of land in Sweden, a burnt boreal forest’s soil has yet to recover, a group of researchers recently found. Vegetation within the slow-growing forests had shown no signs of recovery, in part due to decomposition and carbon releases, or soil respiration, in the forest’s soil being significantly impacted by high-intensity fire.
“As forest floor respiration is tightly coupled to tree root activity, it is likely to take many more years before it reaches the levels observed at an unburnt control stand,” the researchers said in their recently published Agricultural and Forest Meteorology Journal paper.
The researchers affirmed that a decline in carbon releases from soil may sound like a positive change in the context of global, greenhouse gas-driven climate change, but the fact misses the forest for the trees. In reality, a lack of soil respiration means fewer trees and other vegetation can grow, turning a once carbon-sink forest into a long-term carbon emitter.
Which trees were logged after the fire also played a large role in the forest’s recovery, the researchers said. The logging of living trees after low-severity fire led to “immediate and significant” decreases in soil respiration, while the salvage-logging of dead trees after high-severity fire significantly slowed the regrowth of understory vegetation.
“Our results highlight the significant and persistent changes to forest floor carbon fluxes due to fire and choice of post-fire management strategy,” the paper said. “Future work is needed to investigate the interaction effect between fire severity and salvage-logging and to more closely examine the effects of different site preparation methods on post-fire soil carbon fluxes and vegetation recovery in the boreal context.”
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